This disclosure generally relates to a stand-alone mattress having an internal spring system and foldable between an open position in which a user is resiliently supported, and a closed position in which the mattress and the spring system are compactly stored in an item of furniture.
It is generally known that foldaway or foldable beds are attractive bedding options for persons with restricted living space, such as are commonly found in recreational vehicles, trailers, boats, studio apartments, and the like. A Murphy-style bed includes a mattress that can be swung or folded into a wall-mounted cabinet or closet when not being used for sleeping. A convertible foldable bed folds upon itself, either one or two times, for compact storage to serve as a sofa or seating area, and then is unfolded into a bed for sleeping. The convertible sofa-bed includes a mattress that is sufficiently flexible to fold upon itself, and that is supported and deployed by an articulated bed frame.
Although generally satisfactory for their intended purposes, the known foldable beds have exhibited some drawbacks. For maximum sleeping comfort. the mattress is desired to be relatively firm and thick. However, a thick, firm mattress is not readily foldable, and particularly not in furniture of contemporary style where a low seat height and small dimensions are aesthetically desirable. In foldaway beds, a thick mattress requires a deeper cabinet or closet, thereby encroaching on the already limited living space. Where style and space requirements are paramount, a thin, foldable, soft and easily crushable mattress is employed; however, the result is often an unsatisfactory, uncomfortable sleeping surface.
To solve the aforementioned problems, several internal spring systems within mattresses have been developed, the systems being foldable for compact storage and being unfoldable for resiliently supporting a person during use. Reference can be made, for example, to such earlier U.S. patents as, namely, U.S. Pat. Nos. 4,489,450; 4,654,905; 4,620,336; 5,184,809; 5,431,376; 5,535,460; 5,539,940; 5,539,944; 5,540,418; 5,524,305; 5,642,536; 5,655,240; 7,487,564; 7,726,636; and No. 7,979,930.
As exemplified by some of these patents, each internal spring system has an upper wire grid located below, and in close proximity with, an upper mattress face; a lower wire grid located above, and in close proximity with, a lower mattress face; and a plurality of generally planar, sinuous springs, each pivotably connected at its opposite ends to the upper and lower grids. When the mattress is in the open or body-supporting position, the sinuous springs stand vertically upright in parallel planes generally parallel to head and foot end faces of the mattress, and resiliently hold the upper and lower grids apart. However, as the mattress is folded to the closed or storage position, the pivotable springs pivot about the grids and lie in inclined planes; and, at the same time, the upper and lower grids shift longitudinally and are drawn closer together, thereby decreasing the distance between the upper and lower mattress surfaces and decreasing the thickness of the mattress so that it can be compactly stored within the furniture cabinet or closet in the closed position.
Experience has shown, however, that the longitudinal shift between the upper and lower grids is disadvantageous, because this shift must be accommodated in the mattress itself, as well as in the furniture cabinet or closet. For example, if the upper and lower grids have the same length as considered lengthwise or longitudinally of the mattress, then the upper grid would shift longitudinally forwardly during movement to the closed position. The shifted upper grid occupies more space that would undesirably increase the interior space required within the furniture cabinet or closet.
In addition, the known mattresses having such sinuous springs have a tendency to collapse in the open position, that is, they cannot readily stand erect by themselves without having to somehow anchor it to a support outside the mattress to maintain vertical stability, and/or by using internal webbing straps to resist such collapse.